o-Quinonediazide compounds are known to undergo, when irradiated with actinic light, decomposition of the diazo group, forming carboxy group-containing compounds. Therefore, when imagewise exposed and processed with an alkaline developing solution, exposed portions of a light-sensitive layer containing o-quinonediazide compounds are removed. Accordingly the unexposed portions form an image. Thus, the o-quinonediazide compounds have recently been extremely widely used as a so-called positive working light-sensitive component in a light-sensitive PS plate or in a photoresist composition used in photoetching. In particular, a composition prepared by mixing a o-quinonediazide compound with an alkali-soluble resin has been advantageously employed from the stand points of economical and practical merits. Above all, a resin composition prepared by mixing a o-quinonediazide compound with a novolak type phenol-formaldehyde condensate resin or cresol-formaldehyde condensate resin has been popularly used.
Useful developing agents for developing light-sensitive layers containing these o-quinonediazides include aqueous solutions containing sodium tertiary phosphate, sodium hydroxide, sodium silicate, potassium silicate, ammonium silicate, etc. alone or in combination. However, an aqueous solution of sodium hydroxide, sodium tertiary phosphate or the like can exert a strong etching action on a metal such as aluminum depending upon the developing time, thus being inconvenient for developing light-sensitive materials having a metal support. In addition, such aqueous solutions provide extremely varied development results and, in extreme cases, images can be removed by only a slight protraction of developing time. Further, they undergo so much deterioration of developing ability when repeatedly used that the amount of light-sensitive materials processable with a definite volume of the solution (processing capability) is very small. Accordingly, an aqueous solution of sodium silicate or potassium silicate has recently been used with comparative advantages. Because, they exert only a small etching effect on metals and, at the same time, their developing ability can be controlled to some extent by adjusting the ratio of silicone oxide (SiO.sub.2) to sodium oxide (Na.sub.2 O) or potassium oxide (K.sub.2 O) (generally presented as a molar ratio of SiO.sub.2 /Na.sub.2 O or SiO.sub.2 /K.sub.2 O), with the silicone oxides being ingredients of sodium silicate or potassium silicate, and adjusting the concentration thereof. That is, as the content of SiO.sub.2 increases, there results a more suppressed developing ability, with development stability being increased, whereas as the content of Na.sub.2 O or K.sub.2 O increases, developing ability is increased with development stability being decreased. The phrase "development stability" as used herein means stability of image versus developing time. As the content of only Na.sub.2 O or K.sub.2 O increases, removal of the image is liable to take place in a short time.
Processing capability of a definite volume of the developing solution becomes higher as the content of Na.sub.2 O or K.sub.2 O increases. Therefore, moderate processing capability can be obtained together with a certain degree of developing ability and stability by raising the total concentration while adjusting the SiO.sub.2 /Na.sub.2 O or SiO.sub.2 /K.sub.2 O ratio in view of developing ability and development stability. However, this is still insufficient for satisfying both of the requirements: if developing ability is satisfactory, there results insufficient stability and, if stability is satisfactory, there results insufficient developing ability and processing capability. In addition, since a comparatively high concentration is employed, a precipitate is easily formed, and a large amount of acid must be used for neutralizing a waste liquor. The problems with the above-described developing solutions containing sodium hydroxide, sodium tertiary phosphate, sodium silicate, potassium silicate or the like are summerized as follows: Increased alkaline strength leads to insufficient development stability though developing ability and processing capability are increased and, in order to obtain sufficient stability, the alkali concentration must be decreased, which results in insufficient processing capability. Therefore, if sufficient development stability is obtained while maintaining high alkaline strength, there can be obtained a developing solution having excellent developing ability and processing capability. As a process for obtaining sufficient development stability with high alkali strength, Japanese Patent Application (OPI) No. 51324/75 describes adding an anionic or amphoteric surfactant to a developing solution, Japanese Patent Application (OPI) No. 95946/80 describes adding a water-soluble cationic polymer, and Japanese Patent Application (OPI) No. 142528/81 describes adding a water-soluble amphoteric high polymer electrolyte. However, these developing solutions have the defect that, when development is conducted in an automatic developing machine, the developing solutions are liable to foam during development. In addition, Japanese Patent Application (OPI) No. 25100/80 corresponding to Canadian Patent No. 1,145,190 describes adding an ionic compound of a transition element of the group IIA, IIIA or IIIB of the periodic table. Although this addition is effective for suppressing etching of anodized aluminum support with a strong alkali, it fails to attain development stability.